Tomato bacterial wilt is a sudden and serious disease that commonly occurs in summer when temperatures and humidity are high. It primarily affects tomato cultivation in greenhouses, especially during the extension of autumn planting or during the autumn and winter seasons.
Symptoms: Although infections may occur during the seedling stage, no visible symptoms appear at that time. However, as the plant enters the early fruiting stage, the upper, middle, and lower leaves of the infected plants begin to wilt, typically during midday and then recover in the evening. If the soil is dry and the temperature remains high after infection, the plant can die within a few days. The wilting period is very short, and even when the plant dies, it remains green, with only the leaf color slightly lighter—hence the term "green wilt." The roots of the diseased plants, especially the small lateral roots, turn brown and decay. Cutting the base of the stem near the surface reveals that the vascular bundles have turned brown. When pressed, a cloudy mucus is released from the vessels.
Pathogens and Conditions: Tomato bacterial wilt is caused by the bacterium *Pseudomonas aeruginosa*, which infects the vascular system of the plant. The bacteria survive over the winter in the soil or on plant residues and can remain viable for about 14 months. They spread through rain, irrigation water, farming tools, and agricultural activities. The bacteria enter the plant through wounds in the roots or the base of the stem, multiply in the vascular tissues, and spread along the conduits, causing blockages and destruction of the vascular system. This leads to water deficiency and wilting in the plant. High temperatures and humidity favor the development of this disease. Additionally, weak seedlings, continuous cropping, poor root development, low-lying fields, excessive watering, and irregular wet-dry cycles can all contribute to the severity of the disease.
Control Measures: 1. Choose resistant tomato varieties. 2. Cultivate strong seedlings or use grafted seedlings, such as wild tomatoes like CH-Z-26 as rootstock. 3. Use shade nets for summer and autumn seedlings. 4. Chemical control: During the early stages of the disease, apply 50% mancozeb wettable powder diluted 800–1000 times, or 72% streptomycin soluble powder diluted 4000 times, or 50% DT wettable powder diluted 400 times, or 25% copper ammonium solution diluted 500 times. Apply these solutions through irrigation, using 0.3–0.5 liters per plant every 8–10 days, and repeat the treatment 2–3 times. These methods help prevent further spread and reduce the impact of the disease on tomato crops.
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